The present invention relates to a multipurpose product irradiator. More specifically this invention relates to a cartridge product irradiator useful for irradiating medical, food and other products or articles.
Irradiation systems are used for irradiating medical devices, foodstuffs, food utensils, as well as other goods such as cosmetics, waste products and the like. Typically high energy ionizing radiation is used as the radiation source, for example gamma radiation, X-ray, electron beam, or the like. The source, in the case of a radioisotope, is typically maintained beneath the irradiation chamber within a pool when not in use, and raised into position as required. Articles of interest are placed upon pallets, or loaded into unique carrier trays or totes, and these pallets or carriers are conveyed past the radiation source in order to expose the contents therein.
Many prior art irradiators utilize conveyors in order to move a product laden carrier past a radiation source, for example U.S. Pat. Nos. 5,396,074, 5,001,352, 4,866,281, 4,852,138, 4,561,358, 4,481,652, 3,676,675 or 3,564,241. These irradiators utilize a source-overlapping-product configuration, and operate with a low efficiency of source utilization. Furthermore, these systems necessitate the use of many moving mechanical parts within the irradiation chamber, yet the environment within the irradiation chamber is hard on many plastics and metals. Such designs are therefor prone to repeated failures that require full shutdown of the irradiator for repair. Similarly, other transport systems, (U.S. Pat. Nos. 4,066,907, 4,018,348) use turntables coupled with conveyor systems to expose a product to a source. These systems also comprise many moving parts within the irradiation chamber, and necessitate substantial product handling within the irradiation chamber.
Other irradiators have adopted an alternate transport system with which to move a product past a source. In U.S. Pat. No. 5,396,074 there is disclosed a facility for irradiating foods and medical devices using an electron beam as the radiation source. An overhead transport conveyor is used to suspend article carriers to permit their movement around a track and to bring these carriers in front of the radiation source. The suspended article carriers are capable of rotating upon their vertical axes which permits radiation of two sides of a product disposed within the article carrier. This design permits exposure of both sides of the article carrier to the radiation source. However, radiation by electron beam may result in a poor depth of penetration in medium to high density products (i.e. over about 0.4 g/cc), and extensive repackaging is required in order for such products to be treated effectively with a low resulting DUR. This type of irradiator therefore has a limited use. A similar conveying system is found in U.S. Pat. Nos. 4,481,652 and 3,673,409, with carriers that are suspended from a monorail-type track.
U.S. Pat. No. 5,400,382 is directed to irradiating products, located on pallets moved on shuttle cars, with gamma rays. The shuttle cars move the pallets into the region of the gamma source, on a series of parallel tracks, and the pallets are transferred from track to track so that each side of the object being irradiated is exposed. Again, with such a design there are many moving parts located within the irradiation chamber thereby minimizing access for maintenance and repair. Furthermore, these irradiators use a source-overlapping-product configuration which results in a low efficiency of radiation utilization.
Several irradiator designs do not require the introduction of the source into the irradiation chamber, rather the product is lowered into the pool surrounding the source. For example, U.S. Pat. No. 3,676,675 is directed to a subterranean production irradiator with a product conveyor system comprising an endless chain and sprockets arranged to permit movement of specialized product carriers past an radiation source. The product carriers are hung from the chain, and pass over and under the source in a sinusoidal path. A similar approach is disclosed in U.S. Pat. Nos. 4,760,264; 4,908,221; 5,008,550 which incorporates a water-tight duct system through which carriers are passed. The conveyor system comprises a continuous chain in order to move the product through the duct system. In all of these designs, the speed of the conveyor effects all carriers attached to the conveyor, any variation in speed affects all product carriers at the same time throughout the ductwork. Any mechanical problem localized within the subterranean irradiation chamber is also very difficult to repair, and this is complicated by the fact that the source can not be easily removed from the irradiation chamber resulting in time consuming maintenance or repair procedures. Due to the types of carriers employed, extensive product handling in order to load and unload the carriers from, and to, a pallet is required.
U.S. Pat. No. 4,561,358 is directed to an apparatus for conveying elongated articles through a radiation beam. The conveying means comprises two overhead tracks, and a guide that associates with, but is located below the carrier to direct the orientation of the article and permit both sides of the article to be exposed to the radiation source. U.S. Pat. No. 3,564,241 is directed to an irradiation apparatus comprising a continuous horizontal track to form a single path around a radiation source.
U.S. Pat. No. 4,066,907 discloses the use of a turntable with several levels that circumscribes a vertically placed source. This configuration permits the partial exposure of the top and bottom of the product to the source. The product is moved onto the turntable by a goods handling appliance, such as a fork lift coupled with a telescopic table. The same goods handler is also used to transfer product between levels of the turntable in order to permit exposure of the sides and a portion of the top and bottom of the product to the source. All of this material handling takes place within the irradiation chamber. Due to the harsh environment within the irradiation chamber, routine maintenance requires shutdown of the irradiator. The carriers used within such irradiators also require extensive product handling and repackaging in order to load and unload the carriers. These irradiators also employ a source-overlapping-product configuration which results in a low efficiency of radiation utilization.
U.S. Pat. No. 4,864,595 discloses a simplified bulk-loaded product irradiator that utilizes large canisters each containing approx. 10,000 lbs of product that can be loaded directly from a truck into the irradiator.. Large canisters are used so that handling of the product is minimized. However, the use of such large canisters results in a poor dose uniformity within the product itself as products close the outside of the canister receive a much higher radiation dose than those positioned within the canister. The use of large canisters may work well with low density products (medical supplies) where dose uniformity is not important. However, this irradiator is unsuitable for use with higher density products, including food.
Several problems exist with most prior art product irradiators. Many designs require considerable carrier handling within the irradiation chamber either to complete a pass around the source, or to effect a change in the level of turntable or conveyor. As a result of the required carrier handling devices and associated mechanisms, as well as track or conveyor configurations, or carrier designs, there is much support or structure between the source and product within many prior art irradiators. This structure attenuates the radiation emitted from the source and reduces the efficiency of radiation utilization within the irradiator. Furthermore, many prior art irradiators adopt a source-overlapping-product configuration and this further results in an a lower efficiency of radiation utilization. Many prior art irradiators are not capable of attaining a low dose uniformity ratio (DUR) within the product which is required for many products, for example foods. Therefore, these designs are only suited for treatment of products of low density.
The environment within the irradiation chamber is also harsh on components that are subject to repeated radiation exposure including the product carriers, transfer mechanisms, pulleys, bearings and track assemblies. For example, gamma radiation, through cross linking, degrades carbon based, and related materials, including lubricants, plastics, non-metallic seals and the like. Furthermore, when the surrounding air is irradiated, ozone is produced which is a strong oxidant that corrodes ferric metals. Therefor, any suitable product irradiator design should consider minimizing the number of moving parts within the irradiation chamber, as well as permitting the easy removal of components repeatedly exposed to radiation in order to minimize downtime of the irradiator.
Prior art irradiator designs necessitate the assembly of components of the irradiator on-site and within the irradiator chamber, since components are brought into the irradiation chamber typically via a roof plug opening. The size of the roof plug opening limits the size of component that may be brought into the irradiation chamber. Therefore, portions of each component are loaded through the roof plug opening, assembled and tested within the chamber.
The cartridge product irradiator of the present invention sets out to overcome the deficiencies identified within the art, and ensures a relatively even dose uniformity ratio (DUR) in a product over a range of product densities. The cartridges of the cartridge product irradiator allow for easy batch product interchange from the irradiator thereby minimizing the time that the radioactive source is not in use. In addition, the number of moving parts contained within the irradiation environment has been reduced in order to minimize effects of radiation and ozone on these components. Furthermore, most of the moving parts spend a substantial portion of time outside the irradiation chamber, which extends their use, reduces maintenance, and provides for easy access, repair and replacement thereby minimizing down time of the product irradiator. Due to the use of hot cell door, large component parts may be manufacture and tested off-site prior to installation within the irradiation chamber. This increases efficiency of, and reduces costs associate with, irradiator construction.
The present invention relates to a multipurpose product irradiator. More specifically the invention relates to a cartridge product irradiator useful for irradiating medical, food and other products or articles.
According to the present invention there is provided a cartridge product irradiator comprising an irradiation chamber, a cartridge feed system, and a tote transfer system. The cartridge in addition to comprising totes may further comprise a movable chassis for translocating the cartridge into the irradiation chamber. Similarly, the cartridge may also comprise a bed which may be disengaged from the cartridge. The bed may be loaded with carriers or totes containing products at a remote location and be transported to, and engage with, the movable chassis of the cartridge, which subsequently translocates the cartridge into the irradiation chamber. Once inside the irradiation chamber the totes may be rearranged on the bed using a conveying system and the tote transfer system during irradiation processing.
This invention is also directed to a cartridge product irradiator as defined above wherein the tote transfer system comprises pushing systems for pushing carriers or totes along the conveyor system and transfer elements for receiving totes displaced by the pushing system and reorienting the totes along a different row from which the totes were displaced thereby rearranging the totes during irradiation processing. The pushing system may comprise pistons that are pneumatically or hydraulically controlled.
This invention is also directed to a cartridge product irradiator as defined above wherein the tote transfer system is attached to the movable chassis of the cartridge comprises.
This invention is also directed to a cartridge product irradiator as defined above wherein the tote transfer system additionally comprises a tote lifting means to vertically reposition a tote from a first to a second level.
The invention is also directed to a cartridge product irradiator wherein the radiation chamber comprises a radiation source, which may be a gamma radiation source. If the radiation source is a gamma radiation source then the gamma radiation source may be cobalt 60 or cesium 137. This invention also embraces a product irradiator, defined above, wherein said irradiation chamber is temperature controlled and ranges from about xe2x88x9225xc2x0 C. to about 25xc2x0 C.
The present invention also pertains to the cartridge product irradiator, wherein the movable chassis comprises a translocation system to permit movement of the movable chassis.
The product irradiator of the present invention overcomes many of the problems identified within the prior art. The number of moving parts exposed to the irradiation chamber environment is reduced in order to minimize effects of irradiation and ozone on the components. Furthermore, the duration of exposure of such moving parts is reduced within the irradiation chamber. The design of the present invention also permits easy removal of components from the irradiation chamber for repair thereby minimizing down time of the product irradiator. The carriers or totes containing the product irradiator of the present invention are designed in order to minimize or eliminate product repackaging, and ensures that palleted goods can be placed onto appropriately sized carriers and, following treatment, can be easily repalleted. These features result in a greater product throughput, and flexibility in the use of the irradiator, permitting a variety of products to be treated. In addition, the cartridge product irradiator of the current invention also permits efficient radioactive source utilization.
The product irradiator as disclosed herein also provides for a improved method of construction of irradiator that allows large pre-manufactured components to be assembled off-site and factory tested, and then installed within the cartridge product irradiator. This improved manufacturing method is possible due to the large entrance into the irradiation chamber provided by the hot cell door.
This summary of the invention does not necessarily describe all necessary features of the invention but that the invention may also reside in a sub-combination of the described features.